add functions to compute the range and dE/dx for muons in water

1 files changed, 154 insertions, 0 deletions

diff --git a/muon.c b/muon.c
new file mode 100644
index 0000000..ab79666
--- /dev/null
+++ b/muon.c
@@ -0,0 +1,154 @@
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_spline.h>
+
+static int initialized = 0;
+
+static double *x, *dEdx, *csda_range;
+static size_t size;
+
+static gsl_interp_accel *acc_dEdx;
+static gsl_spline *spline_dEdx;
+
+static gsl_interp_accel *acc_range;
+static gsl_spline *spline_range;
+
+static int init()
+{
+    int i, j;
+    char line[256];
+    char *str;
+    double value;
+    int n;
+
+    FILE *f = fopen("muE_water_liquid.txt", "r");
+
+    if (!f) {
+        fprintf(stderr, "failed to open muE_water_liquid.txt: %s", strerror(errno));
+        return -1;
+    }
+
+    i = 0;
+    n = 0;
+    /* For the first pass, we just count how many values there are. */
+    while (fgets(line, sizeof(line), f)) {
+        size_t len = strlen(line);
+        if (len && (line[len-1] != '\n')) {
+            fprintf(stderr, "got incomplete line on line %i: '%s'\n", i, line);
+            goto err;
+        }
+
+        i += 1;
+
+        /* Skip the first 10 lines since it's just a header. */
+        if (i <= 10) continue;
+
+        if (!len) continue;
+        else if (line[0] == '#') continue;
+        else if (strstr(line, "Minimum ionization")) continue;
+        else if (strstr(line, "Muon critical energy")) continue;
+
+        str = strtok(line," \n");
+
+        while (str) {
+            value = strtod(str, NULL);
+            str = strtok(NULL," \n");
+        }
+
+        n += 1;
+    }
+
+    x = malloc(sizeof(double)*n);
+    dEdx = malloc(sizeof(double)*n);
+    csda_range = malloc(sizeof(double)*n);
+    size = n;
+
+    i = 0;
+    n = 0;
+    /* Now, we actually store the values. */
+    rewind(f);
+    while (fgets(line, sizeof(line), f)) {
+        size_t len = strlen(line);
+        if (len && (line[len-1] != '\n')) {
+            fprintf(stderr, "got incomplete line on line %i: '%s'\n", i, line);
+            goto err;
+        }
+
+        i += 1;
+
+        /* Skip the first 10 lines since it's just a header. */
+        if (i <= 10) continue;
+
+        if (!len) continue;
+        else if (line[0] == '#') continue;
+        else if (strstr(line, "Minimum ionization")) continue;
+        else if (strstr(line, "Muon critical energy")) continue;
+
+        str = strtok(line," \n");
+
+        j = 0;
+        while (str) {
+            value = strtod(str, NULL);
+            /* According to the file, the values are stored for wavelengths
+             * between 230 and 700 in 1 nm increments. */
+            switch (j) {
+            case 0:
+                x[n] = value;
+                break;
+            case 7:
+                dEdx[n] = value;
+                break;
+            case 8:
+                csda_range[n] = value;
+                break;
+            }
+            j += 1;
+            str = strtok(NULL," \n");
+        }
+
+        n += 1;
+    }
+
+    fclose(f);
+
+    acc_dEdx = gsl_interp_accel_alloc();
+    spline_dEdx = gsl_spline_alloc(gsl_interp_linear, size);
+    gsl_spline_init(spline_dEdx, x, dEdx, size);
+
+    acc_range = gsl_interp_accel_alloc();
+    spline_range = gsl_spline_alloc(gsl_interp_linear, size);
+    gsl_spline_init(spline_range, x, csda_range, size);
+
+    initialized = 1;
+
+    return 0;
+
+err:
+    fclose(f);
+
+    return -1;
+}
+
+double get_range(double T)
+{
+    if (!initialized) {
+        if (init()) {
+            exit(1);
+        }
+    }
+
+    return gsl_spline_eval(spline_range, T, acc_range);
+}
+double get_dEdx(double T)
+{
+    if (!initialized) {
+        if (init()) {
+            exit(1);
+        }
+    }
+
+    return gsl_spline_eval(spline_dEdx, T, acc_dEdx);
+}